[Leica] Fw: lens design philosophies (2)

["Erwin Puts" <imxputs@ision.nl>]

It is very sensible for a designer not to try to optimize a lens beyond the
level that the mechanical tolerances can allow for.
Some people have objected to my remarks that many Cosina lenses show
decentred elements as it has been interpreted as Cosina-bashing.  It is not.
Some older Leica lenses show this decentring too: it is the consequence of
the tolerance level that is accepted or defined as the level of precision
that is required for a given level of image quality or a given level of
manufacturing precision.
A designer and the company in which (s)he works knows what is possible or
required and engineering is not sorcery: any additional minute of work costs
money and more checks and frequent adjustments cost money too.
Generally Cosina lenses are very good and surpass many of the older Leica
designs. That is the power of modern computer programs and improved
manufacturing technology.
An intriguing question is this: do Cosina lenses show significant
differences when stopped down to Leica lenses stopped down to the same
aperture.
My simple answer is yes. The advantages of Leica lenses are its tighter
tolerances, use of better quality glass, advanced optimization and this
shows at all apertures in higher micro contrast, higher transparancy (finer
reproduction in high lights and shadow areas), lower level of residuals
(finer differentiation of hues and tones in small details), greater fidelity
of reproduction etc. All of this over the entire (or most of it) picture
area.
There is a diminishing return of course and at f/11 it would be quite
difficult to see the difference.

Here one has to insert a few caveats.

If the photographer is not sensitive to subtle differences and does not do
his own careful comparisons, these aspects may escape him/her. Listen to an
orchestra conducted by two different directors and playing the same piece of
music!. Some will here the differences immediately and some will not. A
trained ear is needed. So is a trained eye.

If the photographer's technique is sloppy or careless or if the material
used is not up to the demands of the lens, many differences will be washed
away by the generally very high noise level of the imaging chain.

My view is this: the Cosina lenses deliver amazingly good image quality and
many users will be served very well by this range of lenses, which expands
at a remarkable speed.   Generally they offer better imagery than many Leica
lenses of the previous generation. Any one who raves about his Summicron DR
should try the Nokton 1.5/50 and get an insight in optical progress made
possible by current desighn programs and optical theory.
Current Leica designs have a clear edge and you can appreciate that if you
are willing to invest some time in the study of their characteristics.
It is easy to gulp down a glass of superb wine and not note the difference
in taste when compared to a cheaper wine. As any wine lover will tell you:
take your time and chew!



Erwin